The current evolution in environmental matters is leading in the fields of energy and chemistry toward favoring the exploitation of natural raw materials originating from a renewable source.
An example of an industrial process using a fatty acid as starting material to is that of the manufacture, starting from ricinoleic acid extracted from castor oil, of 11-aminoundecanoic acid, which is the basis for the synthesis of RILSAN®. This process is described in the book “Les Procédés de Pétrochimie” by A. Chauvel et al. published by Editions TECHNIP (1986). 11-Aminoundecanoic acid is obtained in several steps. The first consists of a methanolysis of castor oil in basic medium, producing methyl ricinoleate, which is then subjected to a pyrolysis to obtain, on the one hand, heptanaldehyde and, on the other hand, methyl undecylenate. The latter product is converted into acid form by hydrolysis. The acid formed is then subjected to a hydrobromination to give the ω-bromo acid, which is converted via amination into 11-aminoundecanoic acid.
The literature contains very few documents describing the synthesis of compounds of amino acid type from natural fatty acids. Beyond the reference cited above, the Encyclopedia of Chemical Technology, 4th Edition, John Wiley & Sons, (1996) Volume 19, page 501, discloses a synthetic route for the production of a “Nylon-13” obtained by polymerization of a lactam obtained from erucic acid produced, for example, from rapeseed. This synthetic route proceeds via an oxidation, for example via ozonolysis, to produce a diacid containing 13 carbon atoms, brassylic acid. After a series of chemical transformations, the lactam 13 may be prepared from brassylic acid. The lactam 13 is then polymerized in the same manner as the lactam 12, which itself has been obtained hitherto from petroleum derivatives. This polyamide containing 13 carbon atoms appears to have properties similar to those of the polyamides 11 and 12.
The process for synthesizing 11-aminoundecanoic acid that has been performed industrially for several decades is satisfactory on the whole. However, it presents a certain number of drawbacks. The first drawback is that its implementation is in practice governed by access to a specific raw material, castor oil. Furthermore, castor oil contains a toxin: ricin, which is extremely toxic and which it is necessary to remove. The second drawback is associated with the reagents used, in particular ammonia and bromine, which require expensive precautions for storage and use. The process co-produces not only glycerol, but also many by-products that have to be upgraded separately: heptanaldehyde, esterol (mixture of untracked fatty acid esters).
Moreover, it is important to have available processes for synthesizing the entire range of long-chain ω-amino acids that may be used in industry, and especially in the polymer industry.
The problem is thus that of finding a process for the synthesis of long-chain ω-amino acids from very widely available, and thus inexpensive, renewable raw materials, which is simple to perform while at the same time avoiding the environmental constraints mentioned previously.